Wafer Plane Inspection with Soft Resist Thresholding

摘要

Wafer Plane Inspection (WPI) is an inspection mode on the KLA-Tencor TeraScanTM platform that uses the high signal-to-noise ratio images from the high numerical aperture microscope, and then models the entire lithographic process toenable defect detection on the wafer plane[1]. This technology meets the needs of some advanced mask manufacturersto identify the lithographically-significant defects while ignoring the other non-lithographically-significant defects. WPIaccomplishes this goal by performing defect detection based on a modeled image of how the mask features wouldactually print in the photoresist. There are several advantages to this approach: (1) the high fidelity of the imagesprovide a sensitivity advantage over competing approaches; (2) the ability to perform defect detection on the wafer planeallows one to only see those defects that have a printing impact on the wafer; (3) the use of modeling on the lithographicportion of the flow enables unprecedented flexibility to support arbitrary illumination profiles, process-windowinspection in unit time, and combination modes to find both printing and non-printing defects. WPI is proving to be avaluable addition to the KLA-Tencor detection algorithm suite.